The present invention relates generally to a UV phototherapy apparatus and method for treatment of dermatoses or skin disorders such as psoriasis, vitiligo, eczema, rosacea, alopecia, and the like, and is particularly concerned with a targeted UV phototherapy apparatus and method in which radiation is applied to successive specific areas of a lesion.
Phototherapy is the use of ultraviolet radiation to achieve therapeutic benefit to dermatoses (psoriasis, vitiligo, rosacea, alopecia, eczema). The UV spectrum is divided into UVA (320-400 nm), UVB (290-320 nm) and UVC (100-290 nm). The UVA region is considered the longwave UV spectrum responsible for tanning effects, the UVB region is considered the sunburning region (erythemal region), and UVC is considered the germicidal region. Typically, both UVA and UVB radiation have been used for treatment of dermatoses. Treatment with UVA radiation is called photochemical therapy and involves the use of a photosensitizing agent, psoralen, and the administration of UVA radiation. The basis for phototherapy is believed to be the direct interaction of light of certain frequencies with tissue to cause a change in immune response. U.S. Pat. No. 5,696,081 of Ulirich describes the immune response caused by UVA and UVB radiation.
Phototherapy has a long history of treating psoriasis dating back to 1926 when natural solar treatments such as the Goekerman regimen and Heliotherapy (sunlight rich in UVB at the Dead Sea) were practiced. Heliotherapy is still practiced today. However, these natural solar treatments have mostly given way to modern booths or chambers that provide artificial UVA and/or UVB radiation. Although the benefits of UVA and UVB are known in dermatoses treatment, the adverse affects upon healthy tissue, particularly of UVB radiation, are also well known and a medical concern.
Most of the devices designed for phototherapy, both in the UVA and UVB, are table top projectors for irradiating the face or feet, or booth or chamber types of devices (solaria). Various UV booth apparatuses are revealed in U.S. Pat. Nos. 4,095,113, 4,103,175, 4,100,415, 4,703,184, 4,177,384, 4,959,551, 4,469,951 and 4,309,616. All of these devices rely upon tubular fluorescent or tubular mercury bulbs as UV sources. The booths are generally composed of multiple banks of bulbs, and irradiate large areas, usually the whole body. Large unaffected portions of the body can be protected with draping or wrapping materials, but this is impractical for most clinical use. The large area (whole body or limb) radiation pattern of these devices is a result of the emission characteristics of the light sources. The diffuse, lambertian emission patterns from these elongated, cylindrical bulbs are difficult to aim or direct to specific areas. To achieve sufficient radiation levels to provide therapeutic affect, large numbers of bulbs are required to achieve treatment times within practical limits. It is common for a booth to have 24 to 48 bulbs to achieve these practical fluence levels.
Generally, the dose of UVB radiation administered in a booth is limited by erythemal (sunburning) action. The absolute amount of UVB that a given person can tolerate before burning varies by skin type and prior exposure. It also varies with the composition of the UVB, because shorter wavelengths have greater erythemal activity. Normally, before treatment is given, the minimum erythemal dose (MED) for each patient is determined by applying different radiation doses in small patches to healthy tissue. These patches indicate the amount of energy (usually expressed in mj/cm2) that will result in sunburning the patient. It is typical for the patches to be viewed at 24 hours, and the patch that is slightly pink is considered the MED level. A single booth treatment starts at some percentage (often 70%) of this MED, and then may be increased in follow up sessions as tolerance builds up due to tanning. A typical cycle of treatments for therapeutic success in a booth is 15 to 30 treatments, usually administered in 2 to 3 treatments per week. The amount of radiation given in a given session is limited by the radiation exposure of the healthy tissue. Sunburning the entire body is not only painful, but also medically unwise.
A similar technique is used for UVA treatment, but the dose is called the MPD and the reading is generally 72 hours after exposure. In both cases, however, the MED or MPD is determined by radiation on healthy (non-lesional) tissue.
Much of the UVA therapy has been replaced by PUVA therapy, called photochemical therapy, where the photosensitizer psoralen or one of its derivatives used with UVA radiation. PUVA treatment has proven to have long term oncological manifestations not seen with UVB treatment. However, when UVB treatment has not been successful, the alternative of PUVA does provide relief, albeit at a potential health risk.
It has been demonstrated that some lesional tissue (psoriatic plaque for example) can withstand much more UVB radiation than healthy tissue. This is largely due to the thickness of the plaque areas. However, the radiation delivered to the plaque in booth therapy is limited to the amount of radiation that the adjacent health tissue can withstand. There are three negative aspects of booth UVB treatment. First, the radiation is provided to both healthy and lesional tissue, thus increasing the total body UVB exposure. It has been demonstrated that this cumulative total body exposure has carcinogenic implications. Second, the low radiation threshold of healthy tissue limits the amount of radiation that may be delivered per session to the lesional areas. This sub-optimal dosage results in an increased number of treatments to achieve the cumulative lesional radiation required for therapeutic success. Third, the increased number of treatments that result from low plaque doses again increases the total body radiation received.
The article entitled xe2x80x9cAction Spectrum for Phototherapy of Psoriasisxe2x80x9d, by John A. Parrish, M.D. and Kurt F. Jaenicke, B.A., published in the Journal of Investigative Dermatology, Vol. 76, No. 5, p. 359-362 (1981) describes the psoriasis action spectrum from 253 nm to 313 nm. The results in this article indicate that radiation below 296 nm is highly erythemal but not therapeutic. The article also reports that the level of radiation to deliver 1 MED at 300 nm is about {fraction (1/10)} the radiation level required to achieve 1 MED at 313 nm. This confirms the higher erythemal activity of shorter wavelength UVB. Conventional UVB fluorescent sources provide UV radiation from 275-340 nm, a result of the fluorescent material bandwidth, and hence provide significant radiation of erythemal activity without therapeutic affect. Since a high proportion of this conventional flourescent radiation is non-therapeutic, but erythemally limiting, it necessitates a larger number of treatments.
The presence of the erythemally limiting but non-therapeutic radiation from conventional sources has led to the development of more effective UVB lamps for phototherapy. Sources of monochromatic radiation at 308 nm are available in the form of excimer lamps (U.S. Pat. No. 5,955,840). Also, tubular fluorescent lamps nearly monochromatic output at 311 nm (U.S. Pat. No. 4,354,139) are available. Both these lamp sources suffer from the disadvantages of large area radiation, i.e. erythemal limits per treatment and healthy tissue radiation. However, many reports are available on the advantages of monochromatic UVB from these lamps. One advantage is the lack of non-therapeutic, erythemal radiation below 296 nm. This allows more of the delivered UVB radiation to be of therapeutic value before the MED is reached. Conventional UVB bulbs which operate in the broad range of 275-340 nm may provide undesirable radiation which promotes cellular proliferation.
As opposed to this large area radiation, targeted phototherapy is the application of radiation to specific areas, defined by the geometry or exit aperture of a delivery device. The radiation dose is generally, although not necessarily, constant through out the application to a lesion. The dose administered during an irradiation cycle is known, and the boundary of the irradiated area is known. It may be thought of as placing a penlight against the skin. The area is known to be the exit area of the penlight, and, in the case of targeted phototherapy, the dose may be controlled. Repeating this pattern of the penlight exit face over a lesion allows for complete coverage of the lesion. Tubular fluorescent lamps in general cannot be effectively used for targeted radiation delivery. This is due to the difficulty in collecting the light from these elongated, diffuse sources, and focusing it onto the skin or into an optical guide. Targeted, or spot delivery of radiation in general requires that the light source be collimated or be of a small intense arc that allows efficient fiber optic coupling. Targeted UV phototherapy systems typically employ lasers and are very expensive.
Monochromatic radiation at 308 nm can be provided by xenon chloride excimer lasers, and such sources are capable of directed site delivery as a result of their coherent beams. The disadvantage of such sources is the high cost of equipment and associated maintenance. They nominally sell in the hundreds of thousands of dollars, and contain high-pressure toxic gases that must be regularly exchanged.
It is an object of the present invention to provide a new and improved apparatus and method for targeted UV phototherapy of skin disorders.
According to one aspect of the present invention, a UV phototherapy apparatus is provided which comprises a base unit having an output port for delivery of UVB radiation within a predetermined range, an optical guide having an input end connected to the output port of the base unit and an output end, and a handpiece having an input end connected to the output end of the optical guide, and an exit aperture of predetermined, non-circular shape for delivering radiation to a target area of a patient, the base unit including a UVB lamp for emitting UVB radiation in a predetermined range, a focusing device for focusing the radiation from the UVB lamp along an optical path onto the input end of the optical guide, and a beam isolating assembly in the optical path for isolating UVB radiation from the lamp in the predetermined range from the remainder of the lamp output whereby at least 90% of the radiation directed into the optical guide is in the predetermined range:
In one example, the predetermined UVB range was between 300 nm and 320 nm. The beam isolating assembly may comprise at least one UVB reflective dichroic mirror for reflecting radiation in the range from 300 nm to 320 nm along the optical path while transmitting substantially all radiation outside the desired range. In a preferred embodiment, two UVB reflective dichroic mirrors are arranged in series along the optical path, for further reduction of unwanted radiation. In one embodiment of the invention, the base unit is provided with a first output port for UVB radiation and a second output port for UVA radiation. A first optical guide and handpiece are connected to the first output port, and a second optical guide and handpiece may be connected to the second output port. The beam isolating assembly includes a mechanism for isolating UVB radiation in a predetermined range and directing the isolated UVB radiation to the first output port, and a mechanism for isolating UVA radiation in a predetermined range and directing the isolated UVA radiation to the second output port. This provides for optional directed UVB therapy with the first handpiece or directed UVA therapy or photochemical therapy using the second output port and connected handpiece.
The UVB lamp is preferably a medium pressure, short or medium arc mercury lamp such as a mercury, xenon mercury, or doped mercury short arc lamp. This type of lamp has the highest proportion of its output in the 300 to 320 nm. UVB and has an output which can be readily and accurately directed by a focusing assembly into the input end of an optical guide of small dimensions, unlike a tubular fluorescent lamp.
The handpiece in one embodiment includes beam shaping optics for expanding the circular beam output from the optical guide into a larger, square beam. The handpiece may be a square tube with polished inner walls, in one example. The square beam output allows for successive side-by-side treatments of adjacent areas of a lesion without any overlap between treatment areas.
According to another aspect of the present invention, a method of treating lesional tissue with targeted UVB radiation is provided, which comprises directing radiation from a UVB lamp source along an optical path, isolating radiation in a predetermined UVB range from the radiation spectrum emitted by the lamp source and directing the isolated UVB radiation into one end of an optical guide,.and connecting the other end of the optical guide to a handpiece having an exit aperture of predetermined, non-circular shape for directing the isolated radiation onto a predetermined target area of tissue to be treated.
Up until now, the only effective devices for applying targeted phototherapy to specific areas of lesional tissue, without applying unwanted radiation to healthy skin in surrounding areas, used a xenon chloride excimer laser as the UVB light source. These devices are large and extremely expensive, require frequent maintenance, and use high-pressure toxic gases, such that these devices can typically only be used in a doctor""s office, and cannot be used by the patient at home. The apparatus and method of this invention provides targeted UVB phototherapy using a much smaller apparatus and an inexpensive UVB lamp as the radiation source. The apparatus is much less expensive, requires less maintenance, and can conveniently be used by a patient at home.